NEW YORK — Years ago, when mixed martial arts was still illegal and Dana White was traveling the country to sell his vision of a different fighting organization, he told anyone who would listen the same thing: The sport is so great, White said, because anything can happen at any time and there are so many ways to win, and lose a bout.

Israel Adesanya, one of the great middleweights in the sport’s history, found that out the hard way.

He was ahead on all three cards, 39-37, after four full rounds Saturday in the main event of UFC 281 at Madison Square Garden, and had nearly finished Alex Pereira at the end of the first round. He appeared all but certain to win a decision and make yet another successful title defense.

And then, things changed, dramatically. The vision that White sold ad nauseam in 2001, 2002, 2003 and even 2004 came back to haunt Adesanya and end his middleweight title reign.

Pereira, who scored a pair of kickboxing victories over Adesanya in 2016 and 2017, caught Adesanya with a crushing right hand that began the end of Adesanya’s reign. He followed up with a series of punches that forced referee Marc Godard to stop it.

In only his eighth MMA fight and his fourth bout in the UFC, Pereira became the UFC champion by stopping Adesanya at 2:01 of the fifth round before a stunned crowd of 20,845.

It was Adesanya’s fight to win, and the jeweler was likely polishing the gem that would go in Adesanya’s belt to denote another defense when Pereira changed the course of UFC history.

White happened to put the headsets on to hear the corner work between the fourth and fifth rounds. Pereira’s corner — including former light heavyweight champion Glover Teixeira — let him have it and vehemently urged Pereira to pick up the pace.

“It was incredible, something you’d see in a movie,” White said. “I don’t know who it was, but he said, ‘You’re losing! You need to knock him out in this round. Move forward, throw punches in bunches, let your hands go and you’re going to be a world champion in five minutes.’ It was something straight out of a movie.”

Pereira had scored a last-round knockout the last time he faced Adesanya, when they met in Brazil on March 4, 2017, at Glory of Heroes 7. Adesanya won the first round, hurt Pereira and scored a standing eight count in the second and then was knocked out by a crushing left hook in the third that night.

For weeks before Saturday’s fight, Adesanya patiently answered questions about his two losses to Pereira and specifically about the knockout. He said it wasn’t in his head and he’d successfully dealt with it.

And he fought that way on Saturday, free, smart and imaginative. He was in command of the fight most of the way, using his lateral movement, his boxing skills and his incredible sense of distance and timing. But Pereira worked hard on calf kicks and it limited Adesanya’s ability to move.

The end came in part, he said, because of “my legs.”

“I was compromised because of the investment he made in calf kicks,” said Adesanya, who also alluded to medical issues which have been plaguing him.

White has repeatedly praised him during his title reign for his willingness to fight anyone, and Adesanya for four-plus rounds was showing why. He’s a skilled, smart and elite fighter and was controlling the bout. Adesanya said he believed he was going to stop Pereira.

But he expressed no regrets. “A lot of guys talk publicly and say they want to fight this guy or that guy, but behind the scenes, it’s a different story,” White said. “Believe me, he wanted this fight. He’s a stud.”

Pereira, though, is also a stud. The guy is still learning the sport, and is a relative newbie, but he took out one of the UFC’s greatest champions when he was trailing and things were looking bleak.

Adesanya now has a long road back, though he said he wants a rematch. Though the kickboxing fights weren’t in the UFC, he’s now 0-3 against Pereira. White said he hadn’t made up his mind, but he clearly was leaning toward granting Adesanya his wish.

But that’s one of the things about the UFC. In a lightweight fight earlier on the card, Dustin Poirier submitted Michael Chandler with a rear naked choke in the third round after fending off Chandler’s choke attempts throughout the second. They won Fight of the Night for their efforts.

The loss dropped Chandler to 2-3 in five UFC fights, though each of them have been memorable battles.

He was talking about the difficulty of fighting so well, and coming so close, and not winning.

He spoke about his own journey, but it could have been about so many other fighters, including Adesanya, as well.

“This is a metaphor for life,” Chandler said.

It was for Adesanya, for sure. While Pereira celebrated, Adesanya met with his team and let them know he was fine. He said he was still lucid and could have continued had the fight not been stopped. He called his family to let them know he was all right.

He did everything right after the fight, like he’d done just about everything right during it.

One mistake, though, and history was changed, just like White said over and over in the early days of this century.

Alex Pereira is the new UFC middleweight champion and once more, Israel Adesanya was left to try to explain the inexplicable.